1. Field of the Invention
This invention relates to a discharge apparatus and a discharge method for discharging a paste-like discharge material and particularly to a technique for stably discharging highly viscous paste.
2. Description of the Related Art
As a technique for forming a wiring pattern on a surface of a substrate such as a glass substrate or a solar cell substrate or forming an active material layer on a current collector surface, a technique for applying paste-like application liquid containing a wiring material or an active material to a substrate or the like is known. For example, an applying apparatus described in JP2013-004400A produces an electrode for battery by applying paste containing an active material and a conductive material to a support body by a die coating method. Further, in this technique, the paste is caused to constantly flow to prevent the cohesion of dispersant added to the paste by recirculating the paste between a tank for storing the paste and a nozzle.
The above conventional technique is for forming a uniform coating film by coating. Although a shearing speed is not clearly specified in the above literature, a numerical value example of 3500 cp (3.5 Pa·s) is described as a typical paste viscosity. On the other hand, to form a fine pattern or thick pattern by such a coating technique, paste having a higher viscosity (more specifically, having a viscosity which is, for example, about 10 to 100-fold of the above numerical value) needs to be used.
At this time, such highly viscous paste needs to be stably discharged at a constant flow rate from the nozzle, but it is not easy to cause the highly viscous paste to reliably flow in a flow path with good controllability and discharge it from the nozzle. Particularly, a technique capable of stable discharge at a low flow rate, which is necessary in forming a fine pattern, has not been established thus far.